Contributed by the Combustion and Fuels Committee of ASME for publication in the JOURNAL OF ENGINEERING FOR GAS TURBINES AND POWER. Manuscript received October 14, 2017; final manuscript received June 17, 2018; published online August 20, 2018. Assoc. Editor: Timothy J. Jacobs. This work is in part a work of the U.S. Government. ASME disclaims all interest in the U.S. Government's contributions.

Abstract

Turbulent spray combustion of n-dodecane was modeled at relevant engine conditions using two combustion models (direct integration of chemistry (DIC) and flamelet generated manifolds (FGM)) and multifidelity turbulence models (dynamic structure large eddy simulation (LES) and renormalization group (RNG) Reynolds-averaged Naiver–Stokes (RANS)). The main objective of this work is to study the effect of various combustion and turbulence models on spray behavior and quantify these effects. To reach these objectives, a recently developed kinetic mechanism and well-established spray models were utilized for the three-dimensional turbulent spray simulation at various combustion chamber initial gas temperature and pressure conditions. Fine mesh with a size of 31 μm was utilized to resolve small eddies in the periphery of the spray. In addition, a new methodology for mesh generation was proposed and investigated to simulate the measured data fluctuation in the CFD domain. The pressure-based ignition delay, flame lift-off length (LOL), species concentrations, spray, and jet penetrations were modeled and compared with measured data. Differences were observed between various combustion and turbulence models in predicting the spray characteristics. However, these differences are within the uncertainties, error, and variations of the measured data.

The uncorrected and corrected pressure-rise at three different locations, location#1 (0,0.053, 0.0806), location#2: (0, 0.05303, 0), and location#3 (0, 0.5303, 0.04), with respect tothe injector; all dimensions are shown in meters. The initial temperature of combustion chamber is 1200 K. DIC and LES were utilized for pressure-rise modeling.

Temperature profile at an initial gas temperature of 1200 K and timing of 0.3 ms after start of injection. The location of auto-ignition is shown by the black circle. DIC and LES were utilized to plot the temperature profile.

Gas temperature rise in the combustion chamber using various thresholds for the maximum number of cells. The vertical lines show the timing at which certain cell count limits were met. The initial temperature of the combustion chamber is 900K. The FGM combustion model and LES turbulence model were utilized.

Corrected pressure-rise at location#1 (0, 0.053, 0.0806) with respect to the injector using various cell sizes. The initial temperature of the combustion chamber is 1200 K. The FGM combustion model and LES turbulence model were utilized. The gray area is the timing of experimental observations of OH* luminosity.

Simulated gas temperature using various cell sizes. The initial temperature of the combustion chamber is 1200 K. The FGM combustion model and LES turbulence model were utilized. The gray area is the timing of experimental observations of OH* luminosity.

Liquid and vapor penetrations of n-dodecane at 1200 K using the DIC model with the two turbulence models. Vapor penetration is based on n-dodecane vapor mass and not all of the fuel vapor intermediate species.

Flame lift-off lengths at an initial gas temperature of 900 K using all combustion and turbulence models. The temperature threshold of 2200 K was utilized for determining the lift-off length at this condition.

Flame lift-off lengths at an initial gas temperature of 1000 K using all combustion and turbulence models. The temperature threshold of 2300 K was utilized for determining the lift-off length at this condition.

Flame lift-off lengths at an initial gas temperature of 1100 K using all combustion and turbulence models. The temperature threshold of 2350 K was utilized for determining the lift-off length at this condition.

Flame lift-off length at an initial gas temperature of 1200 K using all combustion and turbulence models. The temperature threshold of 2450 K was utilized for determining the lift-off length at this condition.

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